Funnel.java revision 7dd252788645e940eada959bdde927426e2531c9 
1/*
2 * Copyright (C) 2011 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
5 * in compliance with the License. You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software distributed under the License
10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
11 * or implied. See the License for the specific language governing permissions and limitations under
12 * the License.
13 */
14
15package com.google.common.hash;
16
17import com.google.common.annotations.Beta;
18
19import java.io.Serializable;
20
21/**
22 * An object which can send data from an object of type {@code T} into a {@code PrimitiveSink}.
23 *
24 * <p>Note that serialization of {@linkplain BloomFilter bloom filters} requires the proper
25 * serialization of funnels. When possible, it is recommended that funnels be implemented as a
26 * single-element enum to maintain serialization guarantees. See Effective Java (2nd Edition),
27 * Item 3: "Enforce the singleton property with a private constructor or an enum type". For example:
28 * <pre>   {@code
29 *   public enum PersonFunnel implements Funnel<Person> {
30 *     INSTANCE;
31 *     public void funnel(Person person, PrimitiveSink into) {
32 *       into.putString(person.getFirstName())
33 *           .putString(person.getLastName())
34 *           .putInt(person.getAge());
35 *     }
36 *   }}</pre>
37 *
38 * @author Dimitris Andreou
39 * @since 11.0
40 */
41@Beta
42public interface Funnel<T> extends Serializable {
43
44  /**
45   * Sends a stream of data from the {@code from} object into the sink {@code into}. There
46   * is no requirement that this data be complete enough to fully reconstitute the object
47   * later.
48   *
49   * @since 12.0 (in Guava 11.0, {@code PrimitiveSink} was named {@code Sink})
50   */
51  void funnel(T from, PrimitiveSink into);
52}
53